End mill cutting tool and indexable insert therefor

Abstract

An end milling tool having a positive axial rake angle in side elevation to facilitate removal of chips from the surface of a workpiece and a curved cutting edge having a neutral (zero) to positive rake angle in bottom plan view as it progressively cuts to enhance chip removal while precluding welding at the work area and enabling the use of a low cutting force. The tool cutting area is formed by a rhomboid-shaped indexable cutting insert at one end having an angular axial rake with a unique curved surface in side elevation provided with a lead corner and a strong included angle in an end elevational view. Other inserts are mounted on the tool above the rhomboid insert to form the remainder of the cutting area and are circular in side elevational view. Each of the rhomboid and circular inserts are mounted in an insert seat having at least one pair of flat side surfaces in abutting relationship with compatible surfaces in the pocket to obtain maximum rigidity in seating and prevent rotation of the insert. The inserts are mounted in adjacent helical rows adjacent to and each having a curved cutting edge portion extending into a helical flute or slot.

I claim: 
     
       1. A helical end mill cutter, comprising a rotary body having an outer periphery, and slots formed in said outer periphery alternately extending fully to the distal end of said body, each of said slots having pocket portions for receiving in staggered sequence therealong a curved rhomboidal rotatable on-edge cutting insert positioned to said fully extending slots distal end, said pocket comprises a seating face for said insert, a threaded aperture centrally disposed on said seating face, a support surface intersecting said seating face and having at least a pair of flat face surfaces with each member's surface parallel to the other for supporting abutment of said inserts.   said curved rhomboidal insert having alternately opposed substantially planar and curved cutting edges disposed about a center,   said cutting edges formed from opposed frusto-conical surfaces,   said cutting edges characterized by radii of curvature displaced from said center, colinear therewith substantially along an insert diagonal,   said insert further positioned on said body in having a portion of one of said curved cutting edges being disposed in said fully extending slot, with a cutting edge corner extending below the bottom plane of said cutter body, and   said curved rhomboidal insert further disposed at a positive axial rake and positive radial rake on said cutter body such that said radial rake proceeds from neutral to positive along said cutting edge upon entering a workpiece,   
     
     
       2. The rhomboidal insert of claim 1 wherein each insert comprises top and underside surfaces, a side wall intersecting said underside surface, and having a least a pair of flat face surfaces parallel to each other and positioned for mating abutment with said flat faces of said support surface in said pocket. 
     
     
       3. The curved rhomboidal insert of claim 2 wherein planar surfaces are laterally disposed one from the other. 
     
     
       4. The helical end mill of claim 1 wherein said curved rhomboidal insert corner extends below said cutter body bottom plane by approximately three degrees. 
     
     
       5. A helical end mill cutter, comprising: a rotary body having an outer periphery, and slots formed in its outer periphery alternately extending fully to the distal end of said body, each of said slots having pocket portions for receiving in staggered sequence therealong rotatable cutting inserts circular in plan providing a plurality of indexable cutting edges in said slot, each pocket comprising   a seating face for said inserts,   a threaded aperture located on said seating face,   a support surface intersecting with said seating face and having at least a pair of flat face surfaces with each inventor's surface parallel to the other for supporting abutment of said inserts,   each circular insert having top and underside surfaces,   a side wall intersecting with said underside surface and having at least three pair of flat face surfaces parallel to each other and positioned for mating abutment with said flat faces of said support surface in said pocket,   each insert tiltable about the longitudinal axis of said cutter body enabling a cutting edge thereof to be disposed at a positive axial and positive radial rake, and said circular insert cutting edges formed from opposed frusto-conical surface.   
     
     
       6. The helical end mill cutter of claim 5 which said fully extending slot abuts said circular insert on said underside face and said side wall surface. 
     
     
       7. The circular inserts of claim 5 wherein said insert side wall includes three pair of flat face surfaces, each member of said pair parallel to the other. 
     
     
       8. A helical end mill cutter, comprising: a rotary body having an outer periphery, and slots formed in its outer periphery alternately extending fully to the distal end of said body, each of said slots having pocket portions for receiving in staggered sequence therealong rotatable cutting inserts circular and rhomboidal in plan, providing a plurality of indexable cutting edges in said slot, each pocket comprising a seating face for said inserts,   a threaded aperture centrally located on said seating face,   a support surface intersecting said seating face and having at least a pair of flat face surfaces with each member's face parallel to the other supporting abutment of said inserts,   each insert having top and underside surfaces,   a side wall intersecting said underside surfaces and having at least a pair of flat face surfaces parallel to each other and positioned for mating abutment with said flat faces of said support surface in said pocket.   each insert tiltable about the longitudinal axis of said cutter body enabling a cutting edge thereof to be disposed at a positive axial and positive radial rake,   said circular insert cutting edges formed from opposed frusto-conical surfaces; and   said curved rhomboidal rotatable on-edge cutting insert positioned to said fully extending slots' distal end, said curved rhomboidal insert having alternatively opposed substantially planar and curved cutting edges disposed about a center, said cutting edges formed from opposed frusto-conical surfaces said cutting edges characterized by radii of curvature displaced from said center, colinear therewith substantially along an insert diagonal,   said insert further positioned on said body having a portion of one of said curved cutting edges being disposed in said fully extending slot, with a cutting edge corner extending below the bottom plane of said cutter body,   said curved rhomboidal insert further disposed at a positive axial rake and positive radial rake on said cutter body such that said radial rake proceeds from neutral to positive along said cutting edge upon entering a workpiece.